Change speed transmission for vehicles



Dec. 8, 1953 w. o, BECHMAN ETAL CHANGE SPEED TRANSMISSION FOR VEHICLES Filed June l0, 1948 NGN Patented Dec. 8, l1953 UNITED STATES CHANGE SPEED TRANSMISSION FOR VEHICLES Application June 10, 1948, Serial No. 32,118

7 Claims.

This invention has to do with a change-speed power transmission apparatus for transmitting power to final drive mechanism of vehicles, and more particularly concerns a type of power transmission apparatus wherein there are a plurality of power transmitting units interchangeably connectable in driving relation with the final drive mechanism.

Power transmission apparatus constructed according to the present invention is particularly adapted for use upon vehicles such as crawler tractors which are propelled and steered by driving propelling units at opposite sides of the vehicle at the same or different speeds. Vehicles of this kind comprise a iinal drive housing wherein there is a final drive mechanism including coaxial iinal drive shafts extending oppositely from a fore and aft center-line position of the vehicle toward opposite sides thereof for respective drive connection with the propelling units at the opposite sides of the vehicle. Such vehicles conventionally comprise a change-speed power transmission unit forwardly of the nal drive casing and having a driven shaft drivingly connected with the two oppositely extending coaxial nal drive shafts in such casing. The change speed transmission unit conventionally includes a main shaft whereon there are gears respectively mated with gears upon a countershaft for driving this countershaft at different speed reduc- 9 tions, and this countershaft constitutes the driven shaft having the driving connection with the nal drive mechanism.

A general object of this invention is the provision of change-speed power transmission apparatus employing a change-speed gearing unit drivingly associated with the final drive mechanism of a vehicle in the above described manner and also employing an auxiliary power transmission unit having a selectively establishable driving connection with the countershaft of the change-speed power transmission unit.

A further object is the provision of power transmitting apparatus of the above character wherein the drive shaft of the change-speed transmission unit is tubular and has a disconnectable driving connection with a main drive shaft disposed concentrically therein and having a drive connection with the auxiliary power transmission unit, there being a disconnectable i driving connection between the auxiliary power transmission unit and the tubular drive shaft of the change-speed transmission unit, whereby said tubular drive shaft and the countershaft can be selectively driven by power transmitted through the auxiliary transmission unit.

ATNT OFFICE A further object is the provision of changespeed transmission apparatus according to the next preceding obj ect wherein the auxiliary power transmission unit is attached to the rear wall of the nal drive casing and is driven by an extension of the main drive shaft which extends across and through the final drive casing, and wherein a driven shaft of the auxiliary power transmission unit is in the form of a tubular shaft concentric with the extending portion of the main drive shaft and extends forwardly through the nal drive casing into driving connection with the tubular drive shaft of the change-speed transmission unit.

A further object is the provision of changespeed transmission apparatus according to the two next preceding objects wherein the auxiliary power transmission unit includes a countershaft structure comprising gears respectively meshed with gears constrained for rotation with rearwardly projecting end portions of the main drive shaft and of the tubular driven shaft of such auxiliary unit, and the ratio of these gears is such as to provide a very slow creeping speed for the vehicle.

A further object is the provision of an auxiliary power transmission unit employing a slip clutch for limiting the amount of torque transmittable through such unit.

Still a further object is the provision of a change-speed power transmission unit and an auxiliary power transmission unit of the aforesaid character, together with an interlocked control therefor making it possible to alternatively connect these units in driving relation with the final drive mechanism but impossible to effect concurrent driving connections of these two units between the main drive shaft and the countershaft of the change-speed transmission unit.

The above and other desirable objects inherent 4 in and encompassed by the invention will be readily comprehended from the ensuing description and claims together with the annexed drawings, wherein:

Fig. 1 is a vertical sectional view taken axially through power transmission apparatus constituting a preferred form of the invention and taken centrally and transversely through final drive mechanism of a steering-by-driving vehicle.

Fig. 2 is a fragmentary transverse sectional View taken on the line 2--2 of Fig. l illustrating transmission controls and an interlock device therefor.

Fig. 3 is a fragmentary plan view showing details of a slip clutch employed in the auxiliary `tending nal drive shafts 2l power transmission unit constituting the lefthand portion of Fig. 1 and taken on the line 3 3 of Fig. 1.

Fig. 4 is a fragmentary plan View taken on the line i-- of Fig. 1 and illustrating a portion of a shifter fork control for the auxiliary power transmission unit.

The power transmission apparatus herein shown is for driving final drive mechanism ifI` contained within a final drive housing I 2. A rear wall of this housing is designated I3 and a front wall thereof is designated ill. The inal drive mechanism includes a conventional large bevel gear I5 driven by a pinion It formed upon the rear end of a splined countershaft I? of a change.v speed power transmission unit E8 which includes a gear box i9 projecting forwardly from the front wall iii of the nal drive casing'. Bevel gear i5 is arranged coaxially with oppositely exof which one is `shown in Fig. 1. These final drivc shafts 2i are drivingly connected with propelling and steering units, such as endless treads of crawler tractors,

`by conventional power transmitting connections which are thought unnecessary to show in conjunction with the disclosure of the present invention.

Normally the nal drive mechanism will bc vdriven by power transmitted solely through the change-speed transmission unit i8, but when it is desired to drive this mechanism, and hence the vehicle at an ultra-slow speed, an auxiliary power transmission unit 22, which is mounted `on the rear wall of the final drive casing l2, will be used in combination with certain parts of the Vchange-speed transmission unit I3.

Referring now to the change-speed transmission unitv I8, it includes a main. drive shaft 25 journaled within bearing units 26 and 2 in the front wall 28 of the gear box. This main drive shaft. has a gear 29 formed integrally with its inner end and also comprises an internally splined recess 3l for meshing with splines upon the front end of a long shaft 32 which is disposed concen- Atrically within an externally splined tubular shaft 33. Inasmuch as the long shaft 32 is constrained for rotation with the main drive shaft 25, said shafts 25 and 32 may be collectively regarded as a drive shaft structure 25-32. The externally splined tubular shaft 33 is rotatively carried at lits forward end in a bearing unit 3s within a recessed end of the main drive shaft gear 2Q and Vis rotatively carried at its rear end within a ball bearing unit 35 carried by the wall la which divides the final drive casing from the gear box l.

Vand therefore constitutes the forward wall of the final drive casing and the rear wall of the gear box.

.A gear 35 splined to the tubular drive shaft 33 carries internal clutch teeth comprising one counv terpart 3l of a jaw clutch 37-98 of which the companion component 3 consists of clutch teeth integral with the teeth of the gear 29. When .the gear 35 Voccupies its most forward position speeds when the drive shaft gears di, 32, and @i3 are. respectively meshed with countershaft gears 34, 45, or 4S. The gears @I and i2 are part of va. gear cluster splined to the shaft 33 and movable axially thereof by a shifter forli (not shown) cooperable with a shifter fork groove 41. The gear d'3, which is splined to the shaft 33, is shiftable to and from meshed relation with the gear d'3 by a shifter fork (not shown) cooperable with a shifter fork groove 4S. Gear lil is shown in a neutral position axially of the shaft 33 and may be slid rearwardly, thatV is', to the left as viewed in Fig. 1, into mesh with one gear of a reversing gear cluster (not shown) of which a second gear of the cluster meshes with countershaft gear 49 to cause reverse drive of the countershaft I'I. This reversing drive for the countershaft is conventional, whereforel it is not illustrated in the drawings.

An alternative driving connection between the main drive shaft 25 and the tubular drive shaf^- 33, employable instead of the clutch 3l-38, com prises a pair of diagrammatically illustrated gear"- 5I and 52 which are respectively meshed with the gear 28 and the slidable gear 35 when the latte is in its rearmost position illustrated in Fig. 1. The gears 5i and 52 are elements of a gear cluster Ell- 52. journaled upon a rod 53 supported at its ends in suitable parts of the gear box. When the gear 36 occupies a neutral position between the position illustrated in Fig. l and its foremost position wherein the clutch 3l-32 is engaged, such gear will be demeshed from the gear 52 and clutch 3l-33 will be disengaged, permitting the main drive shaft 25. to rotate without transmitting power to any of the gears mounted upon the tubular drive shaft33.

Normally the countershaft Il, and hence the final drive shafts 2l of the final drive mechanism, will be driven through gear trains including the various meshable gears upon the tubular drive shaft and the countershaft together with a driving connection through the clutch 3l- 38 or through the gears 2-5I--52-3t- However, when it is. desiredV to drive the final drive shafts 2l at extremely slow speeds, the transmission unit 22 on the rear wall of the final drive casing will be employed in lieu of said clutch 3'I`-38 or the low speed connection including the gear train 29-5-52-3. This auxiliary transmission unit constitutes an alternate speed reduction` means for driving the tubular drive shaft 33 'from the main drive shaft structure 25-32. When the tubular shaft 33 is driven at the extremely slow speeds possible through the auxiliary transmission unit, the countershaft lI and the nal drive shafts 2l will be driven at correspondingly extremely slow speeds which are selectable by selective meshing of the gear pairs @il-M, l'2--i5, and i-l'i It is also possible to drive the vehicle in reverse at an extremely slow speed using the auxiliary transmission unit when the reversing gear d3 is shifted rearwardly from the neutral position shown in Fig. l for connecting the reversing gear cluster (not shown) in series between this gear d3 and the countershaft reversing gear et.

Auxiliary transmission unit 22 includes a separate casing 55 detachably securedto the final drive casing rear wall I3 by a plurality of stud,

bolts 56, of which one is shown in Fig. 1, and nuts 5'! on these bolts. An opening 58 in the forward wall 59 of the auxiliary transmission unit casing contains a ball bearing unit el which registers with an opening 62 in the final drive casing rear wall I 3. Casing bearing units 6I and 62 provide a journal support for a tubular driven shaft 63 which extends forwardly from the auxiliary transmission unit into driving relation with the tubular transmission shaft 33 by means of an internally splined coupling sleeve 64 of which the splines mesh with splines 65 and 65, respectively, upon the rear end of the tubular shaft 33 and upon the forward end of the tubular shaft 63. The long drive shaft 32 is arranged concentrically within the tubular driven shaft 63 and has a journal support on a rear end portion thereof within ball bearing units 61 and 68 mounted Within the auxiliary transmission casing 55. A gear 69 is formed integrally with the rear end of the drive shaft 32, whereas a considerably larger diameter gear 1| is splined at 12to a rear end portion of the tubular driven shaft 63. Gear 69 is meshed with a gear 13 of a countershaft structure whereas the gear 1| is meshed with a gear 14 of the countershaft structure. A slip clutch 15, comprising elements 13 and 11 respectively upon a hub of the gear 13 and splined at 18 to a shaft element 19 of the countershaft structure, constitutes a means for limiting the amount of torque transmittable from the gear 13 to the shaft element. A jaw clutch 8| constitutes means for establishing or disestablishing a driving connection between the shaft element 19 and the countershaft gear 14. Jaw clutch 8| comprises an externally splined hub extension 82 of the gear 14, clutch teeth 83 on the shaft element 19, and an internally splined collar 84 axially slidable from the disconnecting position illustrated in Fig. 1 to a clutch engaging position wherein the internal splines of the collar jointly mesh with the teeth on the externally splined extension 82 and the jaw clutch teeth y83.

Opposite ends of the countershaft element 19 are rotatively supported upon the inner races of ball bearing units 85 and 86. The outer races of these ball bearing units are disposed in coaxial opposite end wall openings 81 and 88 of the casing 55. A radially projecting force reaction element 89 formed on an intermediate portion of the shaft element 89 prevents endwise movement of the gear 13 by force exerted by a helical expansion spring 9| for the slip clutch 15. One end of the spring 9| presses against the slip clutch element 11 for impositively pressing diametrically opposite cuniform endwise projecting teeth 92 thereon into respective notches 93 in the element 18. One pair of these teeth 92 and notches 93 is shown in detail in Fig. 3. The left end of the expansion spring 9| reacts against a spring cap 94 of which the hub presses against the inner race of the ball bearing unit 85 which in turn reacts against a vdetachable force reaction element in the form of a nut 95 turned upon a threaded end portion 96 of the countershaft element 18. Thus the detachable force reaction element 95 reacts against the thrust of the spring 9| without any component of the thrust force being exerted through the balls of the ball bearing unit 85.

Engagement of the disconnectable clutch 8| is controlled by a shifter fork 91 of which the shank is attached to and constrained for rotation with a vertical shaft 98. Furcations l! and |02 of the shifter fork 91 straddle the collar 85 and support shifter rollers |03 which project into a circumferential groove |04 of such collar. A detent device |05 cooperates with spaced notches |06` in the lower furcation |02, one of such notches being shown to be impositively retaining the shifter fork 81 in the position for releasing the clutch 8| or in the clutch disengaging position. An upper end portion of the clutch control shaft 98 has an arm |01 connected therewith for imparting rotational movement thereto.

A link |08 pivotally connects between the free end of the arm |01 and an arm |09 projecting radially from the hub of a control lever ||2 for the clutch 8| of the auxiliary transmission unit. Lever hub is pivotally supported upon a shaft |3 which in turn is rotatively supported in a bearing I4 of a bracket |5 and in bearings ||6 and ||1 of a bracket ||8. Bracket ||5 is secured to the upper plate ||9 ofthe gear box by bolts |2|, whereas the bracket ||8 is secured to said cover plate by bolts |22.

A control lever |23 for controlling the position of the shiftable transmission gear 36 is mounted on and constrained for rotation with the shaft |3 as is a shifter arm |24 of which the lower end is disposed within a notch |25 of a shifter rail |26. Said shifter rail is supported for endwise movement by bearings |21 of which one is shown in Fig. 1. A shifter fork |28 depending from the rail |26 cooperates with a groove |29 in the hub of the gear 36 for shifting said gear.

An interlock device |3| is disposed between the two control levers ||2 and |23 for preventing engagement of the clutch 8| in the auxiliary transmission unit excepting when the change-speed transmission gear 36 and clutch element 31 associated therewith are in the neutral position, that is, when the gear 36 is demeshed from the gear 52 and the clutch element 31 is demeshed from the clutch element 38. This device comprises a, cylindrical member |32 slidable axially within a bore E33 in the bracket ||5, said cylindrical member having conical end portions |34 and |35 respectively receivable by conical recesses |36 and |31 respectively within curved faces |38 and |39 carried by the levers ||2 and |23, said faces being curved circumferentially of the shaft ||3. Each of the conical recesses |36 and |31 is disposed circumferentially of the shaft |3 in such a position as to register with the slidable locking member |32 when the transmission connection controlled thereby is in the neutral or disconnected condition. Thus in Fig. 2 it can be observed that while the control lever ||2 is in the position causing the auxiliary transmission clutch 8| to be disengaged the recess-|36 registers with the locking member |32 and thereby permitting such locking member to be slid to the left for accommodating movement of the lever |23 for establishing either the high speed condition with the clutch 31-38 engaged or the low speed condition with the gear 36 meshed with the gear 52. While the lever |23 is in either of the positions meshing the gear 36 or engaging the clutch 31-38, the recess |31 will be out of registry with the locking member |32 and a portion of the at face |39 will be in registry with such locking member, retaining it in a locked position in the recess |36, preventing engagement of the auxiliary transmission clutch 8|.

When the lever |23 is in neutral causing the gear 38 to be disengaged and the clutch 31-38 to be disengaged, the recess |31 will register with the locking member |32, making it possible for the lever ||2 to be rocked for engaging the auxiliary transmission clutch 3|, and pursuant to such rocking of the lever H2, the recess |36 will be moved from registry with the locking member incident to camming the locking member into the recess |31, and a portion of the ilat face |38 will be placed in registration with such 1rocking member for retaining it in the recess |31 and preventing movement of the gear-clutch element 36-31 from its neutral position. A positive retention of the gear-clutch element 36-31 in its neutral :zgeoflgeac position isobtainedbyra detent device `|13 while a notchy |42 in. thel shifter rail |26 receives a spring-pressedball |43 of suchdevice. The ball |43 is received 'by a rail notch- 44 When'the'clutch 3?-33 is engaged, and a raily notch |1351 registers with and receives the ballA M3 when the gear 35 is meshed with the gear 52; Thus the detentI device cooperates with the three notches |53, |44, and |65 for impositivo retention of the gearclutch element 36.-31 in each of its three axially spaced positions.

It willbe observed that the auxiliary transmission unit 22 may be optionally attached to the rear wall of the finaldrive casing |2A for -suppleinenting the. change-speed transmission unit i8. When the auxiliary unit 22 is disassembled from the remainder of theftransmission apparatus, the nuts will be loosened and such unit 22- disassociated from the change-speed transmission unit and the final drive casing by simply withdrawing such unit rearwardly incident to telescopically disconnecting the forwardsplined end of the long drive shaft 32 from the internally -splined section of the main transmission drive closed by a cover plate (not shown). In the absence of the auxiliary transmission unit 22, the change-speed transmission unit t8. will operate conventionally between the main transmission drive shaft and the ring gear I5 of the final` drive mechanism.

The inner end portion of the driveshaft 32A for the auxiliary transmissionv unit 22, that is, the portion of this shaft upon which the gear B9 is disposed, has a rearward power take-oir extension |5| projecting outwardly through a rear wall opening |52 wherein the bearing unit 68 is disposed. A 'threaded section |53l of the drive vshaft 32 for the auxiliary transmission unit 22 has a nut |54 turned thereon against the inner race of the bearing unit 6B to servecomple- .c

mentally with a shoulder |55` of said shaft for resisting endwise movement of the shaft. An apertured cap |56 attached to the rear wall of the auxiliary transmission casing containsan annular sealing unit |51 circumscribing the-shaft.

inasmuch as the auxiliary transmission drive shaft 32 is causedto rotate at all times with the main drive shaft 25, as a constituent of the drive shaft structure 25-3'2, the rearward power takeoff extension |51 will be constantly driven irrespective of which of the power trains Within the main transmission unit I8 or in the auxiliary transmission unit 22 are employed for transmitting driving force to the vehicle. Also, this power take-olf extension |5| of the auxiliary transmission drive shaft will be caused to rotate when none of the aforesaid power trains is connected for the ransmission of power, that is, when both .the main transmission |8 and the auxiliary transmission 22 are in neutral. Therefore, this auxiliary power take-off extension I5| adapts the transmission apparatus for use upon a towing vehicle for drawing a machine therebehind requiring parts of its mechanism to be operated by power transmitted from the power take-off ex- 8 tension |51, and: for these partsfof the machine to be operated' continuously irrespectivey fof whether the towing vehicle is at rest.

Having thus described a` single preferred em.- bodiment oi the invention with t-heviewofr clearly and concisely illustrating the same, we claim-f:

1. Change-speed power transmission 'apparatus for transmitting driving force'to nal drive mechanism of a vehicle, comprising; power transmission units ofv different speed ratio: on respective opposite sides of such mechanism, one of said units including a drivenshaft drivingly connected with the final drive mechanism; a selectively driveable shaft eXt-endingacross-said mechanism for being alternativelyv driven through said units, means for driving the driv-en shaft from said selectively drivcable-:sha-ft, a drive shaft structure also extending -across said mechanism in. driving relation with said'units, and means for selectively conditioning the transmission units for driving the selectively driveable shaft.

2. Change-speed power transmission. apparatus for transmitting.- driving force to nal drive mechanism of a vehicle, comprising power transmission units of dierent speed ratio en respective opposite sides offsuch mechanism, oneof said units including ai drivenv shaft drivingly connected with the-final drive mechanism, a tubular selectively driveableshaft structure extending across said mechanism and between said units, a drive shaft structure for driving said units-and extending through the tubular shaft, means` for driving said driven shaft from the tubular shaft, andv means for selectively conditioningV the transmission units'for alternativelyl driving the tubular sha-it structure therefrom.

3. In a poweri transmission unit employab'le with a vehicle drive mechanism enclosed in- -a housing having opposite wallsV with axially aligned openings, anda` change-speed unit on the exterior -s-ideof one -ofsuch walls comprising a drivefshaft coaxial with the housing wall openings, a tubular shaft coaxial with the drive shaft and rotatable relatively thereto, means-for selectively establishing a' driving. connection between the driveshaft and said tubular shaft, and means for driving said mechanism from the tubuiar shaft; the combination of a transmission casing mountable eXteriorly on the oppositewall of said housing, a pair-0f coaxial inner and outer shafts rotatively supported'in the'casing and projectable through the house openings intoi respective driving connection with said drive shaft andf said tubular shaft, gears in the casing and respectively constrained for rotation with the inner and outer shafts, a countershaft in the casing, independently rotatable gears on the countershaft and respectively meshed with the rst recited gears, and means for establishing or disestablishing a driving connection betweenv the countershaft gears.

4. The combinationv set forth in claim 3, wherein there is an interlocked control manipulatable to selectively establish the driving connection of the drive shaft with the tubular shaft or the driving connection between the countershaft gears only while the other of suchv connections is disestablished.

5. Change-speed power transmission apparatus comprising' a plurality of power transmission units; one of said units including a driven shaft, a-selectively drivable shaft, and means for transmitting drive from the selectively drivaole shaft to the driven shaft; a drive shaftY structure; and controlla-ble driving means having components respectively in said units for alternatively driving the drivable shaft from the drive shaft structure at diierent speeds with respect thereto.

6. The combination set forth in claim 5, Wherein the controllable driving means components are adapted to drive the drivable shaft at different reduced speeds, and wherein the component in the other of said units is adapted to drive the drivable shaft at the lowest of such speeds.

7. The combination set forth in claim 6, wherein the means for transmitting drive from the selectively drivable shaft to the driven shaft is settable to drive the driven shaft at different speeds relatively to the selectively drivable shaft.

WILLIAM O. BECHMAN. NICHOLAS J. PALKOVIC.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Number Name Date Clifford Mar. 28, 1922 Valentine Dec. 28, 1926 Kendall Feb. 2, 1932 Hill Dec. 14, 1937 Kummick Dec. 29, 1942 Stumpf Feb. 16, 1943 Rohkar Nov. 23, 1943 Johnston Aug. 15,1944 Sternberg July 20, 1948 FOREIGN PATENTS Country Date Great Britain Aug. 21, 1908 Germany Dec. 1, 1922 Great Britain June 13, 1940 France Mar. 19, 1922 Germany Aug. 8, 1932 

